Heat-distortion testing apparatus



April 25, 1950 o. H. KALLAS ETAL HEATDISTORTION TESTING APPARATUS 2 Sheets-Sheet 1 Filed April 28, 1945 m Y m. s H M Mb 6 R 0 V w r T l A HfD.. Af un laar 055 Y B Patented Apr. 25, 1950 TED 2504,9325 riEAr-DrsToRTIoN TESTING APPARATUS Danos 11i Kauas and Saul (Granted undeit; the act of March: '3, "18 83;; as amendd Aiu-ib 30, 1928; 370- 0.-- G. 757) This invention "relates to heat-distortiontest ing'machines and more particularly to arr-apparatus for determining the heat-distortiontem peratureorsoftening point of a plastic or plastic impregnated material, namely; the maximum temperature to which such az -mater-ial can be subjected in service;

An object of this inventionisto provide an apparatus for determining the heat-distort-ion temperature or softening: point of' amaterial, 10 wherein means is provided for minimizing-errors due to thermal expansion within the apparatus itself.

A further object is to provide an apparatus affording a substantially frictionless l'oad' application to the specimen under test;

Another object is to protect thespecimen' supporting structure from the deleteribus'effects of intimate contact with th'e heated' liquid'or-fumes of the bath.

A further object is to provide a compact; rigid and easily manufactured device capable ofcarry; ing. out thermal -distortion tests simply and "at curately. x

Further objects and advantagesof thisuinven tion, as well as its construction, arrangement and operation, will be apparent from" the following description and claimsinconnection with theaccompanying drawings, in which;

Fig-.- l is an isometric view :of an embodiment of this invention,and"

Fig. 2 is an explodedview of the bath portions and heating element forming .part :of this invention.

-In Fig. 1, there is shown a vertically disposed load shaft lU'having'a, reduced-diameter upper portion to receive aweight H and a finger-like lower portion I2, said finger-like portions 12 hav-'- ing' a rounded edge l3 which 'will reston "a specimen 14 during the test. The test-specimen- --i;4-- is placed on supports [5 of 'suitable'material with a low: coefficient of thermal expansion such as; for example, invar, said supports l5 being'zsecured to a bottom plate [6. Side-brackets -11 and- 18 are riveted or otherwise fixedly =secured to the bottom plate [6, saidside brackets Mand -I8 extending vertically upwards and-servingnas=xthe supporting members for a guide element 19 which is fixedly secured thereto; The "guide element- 19 has two bores 20 and 2| therein' to guide" the' thermometers-22 and 23-"to' the test specimen lfl and a third bore 24 to permit the finger-like par-" tion 12 topress upon the'test specimen 5M;

The side :brackets- -l I and 18 support thecover' plate 25 which is fixedly secured to the said brackets I! mam b'ythe angle bracketsliiflone oi' which is obscured in-the drawings) riveted or otherwise' secured to the side' brackets H aim- 18 and cover' plate- 25; The cover plate 25-contain's' two apertures 28 (oi'le aperture I being?" obscured by; other stru'cture'lthat serve as thermometer guides and a third larger ap'e'rture 2 9 in the can tr' of the cover plate: 25 to ermit unimpaired verticaLmovement 'of theloadfshaft'l 0; A foiirth opening 30 near a corner 'of the cover -piate =2 5 permits the escape of -fumes froni the bath fio be described late'r) heatihg the specimen *l4 di1r' in'githe test.

Above the cover Y plate 25', twosubstantially U-shaped braces 31 and 32 are rivetedi bbltedbr otherwise :seeured'to" the brackets I and-'18, said braces 1 having bearing-shaft holders 33-- and 34' fixedly: secured thereto in any suitable manner-. Bearing 'shafts 35 and 36} supportingthe bear ings 3 i and- 38;- v are mounted on the biases f 31' and 32 andbearirig-maf-t holders 33- and 34' through openingsin-said'braces and said holders? Th shafts 35' and '3l6 areh'e1d fixedthe supportingmembers 3|, 32'; 33 and 34 'bylb'olts or" other" suitable"means.: 'The bea'r in-gs- 3'1 and 38 press against-the' parallel'=vertrcai channels 39 and i'il in the loacl'shaf-t Ill forming a 'substan tialiy frictionless supp'ort' tor said load" shaft ID} Braces M and-=42; bearing' shaft holder-s23 and" 44, bearings 45 and 66, an d bearing snafts fl and- 48 "similar Y to=- those already; described are secured to the-top-=of-sa-id brackets li and-'18. Two cros'spieces :49 iand fi il having opening-s -ii amt- 52 therein'are boltedor otherwise secured to tl'ie topibraces "41- ai1il i2 and :serve 'asther mometer guides. The ape'rtures and bor'e's in'th'e' guide element IS, the cover plate 15 andcross piees fi 9 ahd -Efl die-substantially in straight liri es so-thatthe thennometers zz and- :23 eanbs in ser'ted' througlr thefabove recited e1ements name=* 1y; guide elements v19; cover'p1ate"25, an'd cros pieces-49 andsome 'rest above the test speci men M:- I

5 lt byameans of a collar 5' l',- claniping fian ge 55 and arm-53a A 'thu rnbsc'rew 'iil serv's' to rel or increase' th'e:grip of the oollar fi l about th i load snait I'll; -A"ri"gid le'dg 58 protru'des ffeir-i thebearing shaft holdi iiif the manger 59 0f the dial gau'ge '53 resting'rfon said ledge 589'- Thevert'i'cal' motion ofth load sliaft lil 'is tansmitte'd to the diaiP-gaugG ESf biit'th pl g restricted' in its downward-' motion b the ge 58, activates the dial gauge 53winches-graduate in thousandths of an inch Of vertical motion.

The bath in which the specimen I4 is placed consists of an outer container 60 and an inner container 6| of suitable material such as, for example, copper, said outer container 60 havin handles 62 (other not shown) attached thereto. The inner container 5| has a raised shelf or tray 63 which rests on the outer container 60 and serves as a seal for the air space between the outer and inner containers 60 and GI, respectively. The raised shelf 63 also supports the cover pla e 25.

The space between the outer and inner containers 60 and BI, respectively, is partly filled with glycerine or other non-volatile fluid having a high flash-point. A vent 64 in the inner container 6| permits the escape'of glycerine (or other suitable fluid) fumes that may arise when heat is applied to the outside container during the testin of the plastic or plastic impregnated specimen [4. Moreover the specimen under test does not come in contactwith any liquid or liquid fumes and is subjected to only dry heat.

The outer copper container 60, with the test assembly and inner container 6| in position, is placed on an electric heater 65 which is controlled by a standard voltage regulator (not shown), said voltage regulator serving to control the heating of the thermal conducting fluid between said inner and outer containers. The leads 61 and 68 are electrical conductors that carry the heating current from the varying voltage device not shown. The standard voltage regulator supplies sufficient heat to raise the air temperature surrounding the specimen at the desired rate, in accordance with the standards prescribed for the test.

,In operation, the test specimen [4 is properly positioned onto the supports I5, and the load shaft l0 presses upon the specimen it through the finger-like element l2. The appropriate weight H is selected and secured to the top of said shaft I0. The collar 54 is adjusted so that the dial gauge 53 is set to zero when the plunger 59 of the dial gauge 53 contacts the ledge 58. The thumbscrew 51 is then turned to fixedly secure the collar 54 to the load shaft I0. .Thermometers 22 .and 23 are inserted into the specimen supporting framework through the guideways provided for them, the mercury bulbs of said thermometers 22 and 23 resting above but not contacting the specimen l4.

The specimen M is now ready for insertion into the bath. The bath parts are assembled, the inner tank 6| being placed into the outer tank 60, said outer tank 60 being partly filled with a non-volatile fluid having a high flash point. The assembled tanks are placed onto the heat supply stand 65.

The specimen supporting framework restricts any further downward motion of the specimen into the tank. The supporting stand for the specimen [4, when inserted into the bath, is completely housed by the inner tank BI and is protected thereby from the harmful efiects of the heated fluid or fumes of said heated fluid.

When all parts have been assembled as described above, controlled heat is applied to the bath by a conventional electric heater which is controlled by a conventional voltage regulator.

The ambient air temperature surrounding the specimen l4 at the time that the specimen [4 has distorted a predetermined amount is read off the two thermometers 22 and 23. If the temperature readings difier slightly, the mean of the two readings is taken.

Prior to Performing the above described test, a standard specification for the test is submitted to the laboratory such as, for example, the following specification written by the American Society for Testing Materials: The test specimen, 5 inches by 0.5 inch by 0.5 inch supported on a 4 inch span as a simple beam, is subjected to a dead weight load of 5.5 lbs. (2.5 kg.) applied at the midpoint of the span. The air temperature surrounding the test specimen is raised from 77:3.6" F. at the rate of approximately 1 F. per minute. When the deflection midway between supports is 0.010 inch during the temperature rise, the specimen is considered to have reached its heat distortion temperature. The apparatus required for this test has been standardized with a A; inch radius for all specimen support and loading edges.

Many slight alterations can be made in this testing apparatus so that said apparatus could be used to make tests conforming to other rigorous specifications. For example, the rate of thermal heating could be other than 1 F. per minute; the size of test specimen I i or weight I I or amount of distortion could be altered. The radii of the specimen supports could be altered by making the supports I5 readily detachable from the base It and using in their stead other readily detachable invar supports having different radii of curvature.

This invention is useful not only in industrial or testing laboratories but also in physical science laboratories of schools and universities because it is simple to operate and maintain, rugged yet reliable, capable of making reasonably accurate measurements of heat distortion and can be manufactured in various sizes.

This invention readfly lends itself to experimental tests because it enables reproducible results to be obtained under standard conditions,

. thereb permitting observations of reasonably accurate deflections versus reasonably accurate temperatures to be plotted on coordinate paper. The graphs thus obtained serve to show the thermal characteristic or characteristics of the specimen tested.

Various modifications and changes can be made in this invention without departing from the spirit and scope thereof as set forth in the appended claims.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. In a thermal distortion testing device, a framework for supporting a test specimen under distorting pressure, a bath consisting of an outer tank and a readily detachable inner tank insertable into said outer tank, an offset rim on the inner tank abutting the rim of the outer tank so as to limit the total entrance of said inner tank into said outer tank, the space between the walls of said tanks providin a space for containing liquid, said framework being received in said inner tank, specimen distortion measuring and specimen temperature measuring means secured to said framework, means mounted in said framework to apply a distorting force to the specimen, and a controlled heat distributing platform for supporting and indirectly transmitting heat to said framework inserted in said bath.

2. In a thermal distortion testing device, a

framework forsupporting a specimen under distorting pressure, a tray having an elevated and offset frame about its border, a walled tank depending from the central portion of said tray, a gas vent in a corner of said tray, a hollow housing partly filled with a thermal conducting fluid and having outside handles thereon, said depending wall tank and tray serving to house and support a portion of said specimen supporting framework, said walled tank being sufficiently smaller than said hollow housing to permit the insertion supporting structure, bearing shafts secured in opposite pairs at right angles to said horizontal braces, circular bearings mounted on said shafts, a vertically disposed cylindrical rod having two longitudinal, parallel, and diametrically disposed channels machined therein for substantially frictionless slidable engagement with said circular bearings mounted on said bearing shafts, readily detachable weight means mounted on the head of said rod, a fingerlike element protruding from the foot of said rod to rest upon the specimen being supported on said specimen supporting posts, a cover lid secured to the substantially U- shaped supporting framework, an inner tank, and outer tank, said inner tank receiving said framework, said outer tank adapted to contain a liquid,

' said cover lid restricting the motion of said supporting framework when said specimen supporting framework is inserted in said inner tank, and

a dial gauge secured to and registering the motion of said cylindrical rod.

4. The invention as set forth in claim 3 and a controlled heat distributing platform for supporting and transmitting heat to said outer tank.

5. In a thermal distortion testing machine, a vertically disposed specimen supporting framework, bearing shafts attached to said framework, substantially frictionless bearings attached to said bearing shafts, a load shaft with vertically disposed guideways grooved therein, said bearings ridin in said guideways and serving to support said load shaft in a vertical position, a heat controlled bath for partially receiving and supporting said specimen supporting framework, means to measure the temperature of the specimen, and means to measure the movement of said load shaft.

6. A thermal-distortion testing device comprising a specimen-supporting framework, means for variably distorting a specimen under test and mounted on said framework, means mounted on.

said framework and adapted for measuring specimen temperature and distortion, a tank for housing said framework, an outer tank housing the first-mentioned tank and being adapted to contain a thermal conducting fluid and a controlled heating stand for supporting and conducting heat to the outer wall of said outer tank.

DANOS H. KALLAS. SAUL A. ELLER. ERNEST DI LIBERTI.

REFERENCES CITED The following references are of record in the file of this (patent:

UNITED STATES PATENTS Number Name Date 989,471 Abraham Apr. 11, 1911 1,184,837 Edgecomb May 30, 1916 1,826,732 Chatillon Oct. '13, 1931 1,952,523 Abbott Mar. 27, 1934 2,066,016 Rossi et a1 Dec. 29, 1936 

